In the related art, a fiber reinforced plastic honeycomb structure is known in which a first cell wall including pitch-based carbon fibers and a second cell wall including PAN-based carbon fibers are used so as to be selectively and necessarily composited (for example, refer to PTL 1). In addition, PTL 1 discloses that when a fiber reinforced plastic formed of pitch-based carbon fibers and a fiber reinforced plastic formed of PAN-based carbon fibers are compared to each other, the former has higher heat conductivity than the latter while the latter has higher strength than the former.